1. Field of the Invention
The present invention relates to antifuse technology. More particularly, the present invention relates to metal-to-metal antifuse structures which may be fabricated using low temperature fabrication processes.
2. The Prior Art
Prior art metal-to-metal antifuses all exhibit the phenomena of switching. When an already programmed antifuse passes a current having a magnitude comparable to the programming current, the antifuse can on occasion switch to an open state. This can create reliability problems in the circuit employing the antifuse as a connecting link. As a result of this problem, current circuit designs utilizing metal-to-metal antifuses employ very large programming currents in order to maintain a high ratio between the programming current and the normal operating current of the circuit. The necessity to utilize large programming currents requires the use of large-sized programming transistors which increase the size of the integrated circuit utilizing the metal-to-metal antifuses.
In addition, antifuse fabrication processes often employ high temperature processing steps. High temperatures above 550.degree. C. are detrimental to aluminum interconnects used in standard integrated circuits.
It would therefore be advantageous to provide a metal-to-metal antifuse which may be fabricated by a process which avoids high temperature steps, and which can be reliably programmed and have a higher immunity to switching.